Deposition of copper oxides on heat insulating material



P. PAWLYK Nov. 16, 1954 DEPOSITION OF COPPER OXIDES ON HEAT INSULATING MATERIAL 2 Sheefs-Sheet 1 Filed 001.. 8, 1951 TQE INVENTOR PETER PAWLYK BY TQM" ATTORNEYS NOV. 1954' P. PAWLYK 2,694, 5

DEPOSITION OF COPPER OXIDES ON HEAT INSULATING MATERIAL Filed Oct. 8, 1951 2 Sheets-Sheet 2 FIG-2 FIG- 3 INVENTQ PETER PAWLYK RNEYS United States Patent DEPOSITION oacorrnn oxmEs- N HEAT INSULATING Peter a lyk, Dayton, Ohio, assignorm The Commonwealth Engineering-Company of ()hi Dayfom, Ohio, a corporation of Ohio Application October 8, 1951', SerialNo. 256,503

1 Claims. cl.- 117*106)" This invention relates to a gasiplatingsystem and process for the production of semi=conductive and nonconductive coatings on insulating materials andto the products produced by the process.

It has been found that electrically resistant layers of high quality may' be produced by the formation of the mixed copper oxides, particularly cuprous oxide, on metallic and. non-metallic bases by contacting the base under carefully controlled conditions, to" be more particularly discussed hereinafter, with copper'acetyla'cetonate in thegaseous state to eifec't decomposition thereof.. The process of formation of the :oxides may be facilitated .by carrying out the decomposition in an oxidizing atmosphere to achieve selective oxidation of any deposited metallic component present as decomposition of the copper acetyl'acetonate occurs;

This invention accordingly contemplates the provision of a unique method .for the attainment of films of mixed oxides of copper on non-conductive materials.

The invention also contemplates the provision of unique resistive elements attained by depositing from the gaseous state mixed oxides of copper on n'on-condu'c- 1 tive base materials. I

I The method of invention is practicedby heating a dielectric base material to' a temperature range below that at which copper acetylacetonate will decompose to copper metal and contacting the base'mate'rialwith heated vapors of copper acetylacetona'te at a rate-'sufficient to" maintain the temperature of the' mate'rial below the said rangeand at a pressure substantially equal to that of the atmosphere. Under these conditions "the plating deposited on the insulating-base will comprise essentially the mixed oxides of copper. 4

The resistance characteristics of the deposited layer, for a given concentration of metal-bearinggas in the plating chamber, will vary with the velocity of gas flow, the higher flow rates contributing to the formation of a greater proportion of the cupric oxide, althoughso'me cuprous oxide will always be present. --Sim'ilarly lower flow rates-may contribute to the formation of more cuprous oxide but the cuprio -pha's'e will'exi'st in the coating.

In the preferred embodiment of the invention the copper .acetyla'cetonate is vaporized from the solid compound by contactingthe heatedsolid with a heated inert gas, which gas carries the inetal-befarin'g' vapors to a plating chamber. The copper acetyl'a'cetonate decomposes at approximately 455"" F. and accordingly the temperature of the solid compound and theine'rt carrier gas must be maintained considerably below this temperature point. 7 g

The platingchamber to which the heated-.g'asmixfure is carried'isitself heated; and the arrangement thereof is such that the workpiece therein which is to be plated is at a lower temperature than the atmosphere s'ur'rou'nding-it. This is accomplished by exposing the workpiece in the'ch'amber only to the heat of the flowing gases-and to radiationfrom the element which treats the chamber; the workpiece is thus heated by radiationto temperature below. that of the atmosphere and is riia mt'ained in this condition by the heated} flowing gases; thetem era ture of the material is' maintained above 450%455 however which is adapted to cause' copper oxides to deposit on the workpiece. The object to be platedis riot itself heat'ed directly as is; seesaw thecustom in the gaSplatingar-t; Preferablycontrol is 'achie if by regulating the temperature or the flowing gases at a poiiit, if,

spaced slightly fromthe-gworkpieeb aiid between the workpiece andplating chamberheater.

The hot gases when they strike the workpiece 05 lower temperature than the-surroundingatmospherewill only partially decompose, --and. dependingmpon the exact conditions of the system' a mixture of cupl-"ous oxide and cupric'. oxide, or a mix-containing gthevo'xides; plus a small amount [of coppermetal willbe' attained. For example, films may be obtained on /2 rihchk diameter ceramic discs with resistances varying; from l0- ohms to substantially infinity; The control-of the resistance isattained primarilyby controlling thz rate of gas-flow over the discs in the plating cham'be'r Control ofthe oxide formation may also be influenced by the bleeding into the,system -of--.s'malla amounts of oxygen which tendsto develop cupric; oxide formation; As the system will contain -.bothcarbon-..dioxide and the carbon monoxide decompositionproduct; care must be exercised to prevent water vapor or any: appreciable amounts of hydrogen, bearing- ;carbom compounds forming in the chamber, fol-mixes of oxygen;,-,carbon .monoxide and carbon dioxidemay be renderedslightly explosive in the presence o'f-sucli; constituents. lNor mally jif the oxygen isint'roduced as dry: air thefpresencezofthe nitrogen of the air will serve as a suthcientlynelfective diluent to preventfany deleterious; reactiojns. I

The invention "will", be more fullyunderstood-=by reference to the following detailed3description and. accompanying drawings, wherein; V

Figure l 1; is a schematic:representation;of the appa; ratusforthe carrying oiutof oney'embodiment-of the invention; s

ld-dgure 2 illustratesaqcarrier-"for the objectsto be plated; an t Figure 3 illustrates schematically apparatus-for the carrying out ofanother embodimeneofi the. invention.

In Figure 1 the major components'of, thesapparatus utilized to carry out the invention areindicat'ed at 1-,- 2, 3 and 4".- -Numeral 1 indicates' a -source, of carrier gas; the numeral 2 a constanttemper'ature bath conta-ining a carburetor and the compounds ito be vaporized; the numeral 3 indicates the platingj;chamber;-, while the numeral 4 designates generally aarrecovfery system;

The tank; 5 of inertqcarrieragas (carbondioxide) is provided with a valve 6; and ilow meter- 34 having connected' thereto a-length of copper=-tubing; which'gpasses to the constant temperature unit: T tubing 7 is woundas' at; 8 into a coil which surroun A he carbw retor 9 and the tubing is itself; connected {into "the lowe'r end of the carburetor. The carburetor 9;and-c;oil 8 are each immersed in oil 10 containedin tank .11 arid maintained at a constant temperature'by means of heater; 12 and the thermostat unit indicated gener y at" 13. Since such therr'nostatsin themselves-age H taileddescription;thereof-will be'giv re V The bathi's also provided with; a; sti-rrr14 actuated through belt 15 by niotor l o'. {The carburetor contains solid layers of copper acetylacetona'te lZ a daleng'thof insulated tubing extendsfirfom. thc t op of the carburetor and passes to the gas plating chainber I9of-platingchamber unit 3. c

The connection between. tubiiig' lll"aiid chamber 19 may be made-through-s pper 20 a l ghafiy suitable means of connectionr'uay be employed, the dnlymequirement being that the seal be gasftigh Q Gas' chamber: I9 is. resistance heating e "'m' energ from a some v I v 19 is an object carrier 22, more clearly s'l'iowii tnFignre-z The carrier 22 consists 0f,;a rack oi insulating material extending' th'e length of] chamber" 1% d having supports thereon for" the carrying of substantially /2 inch diameter! ber 9 d at the remote, end thereof with utle't' in which tubing 25' is secured, thetubin'g' 25 pa's's'irig directly to the re covery system 4 whereit is secured in the bulb of trap 26.

Positioned between the constant temperature bath 2 and the plating unit 3 in the line 18 is a pump 32 for the ingaintenance of a steady flow of gases to the cham- In the operation of the apparatusof invention, to attain a resistive coating having a resistance value of approximately 300 ohms per centimeter, a ceramic disc or discs 23 are inserted on the carrier 22 in the plating chamber 19. The resistance heater 21 is adjusted to supply a temperature of about 600 F. within the chamber 19 at a point approximately A of an inch above the positioned ceramic disc. The temperature of the oil 10 is adjusted to about 375 F.

Under these conditions the valve 6 on tank is open to permit a flow of carbon dioxide of about one liter per minute through line 7 and-coil 8 wherein it is heated to approximately 375 F. The gas then passes into the carburetor where it contacts the copper acetylacetonate. The copper acetylacetonate having already been subjected to a temperature of 375 F. by means of the oil bath will have built up a considerable vapor pressure and the entering CO2 will sweep these vapors out through tubing 18.

As the packingof the copper compound in the carburetor 9 may tend to restrict to some extent the gas flow, pump 32 is actuated to insure of the steady flow of gas to the plating chamber 19. The gases passing into chamber 19 at the flow rate specified will contact the object or workpiece 23 and will tend to maintain the same cool, that is below the temperature of the surrounding atmosphere and below the temperature at the thermocouple 24. The gases under this condition will decompose and deposit on the workpiece, forming a film consisting substantially only of cuprous and cupric oxide. The waste gases together with any undecomposed copper compound will then pass through tubing 25 to the trap 26 where the cooling effect of water 27 will cause the copper acetylacetonate to deposit out from the decomposition vapors, the decomposition vapors themselves then flow on to the atmosphere.

The time of plating of the above noted process is approximately 30 minutes in order to secure a deposit having a resistance of 300 ohms.

In Figure 3 there is shown an embodiment in which there is provided an oxygen inlet to the system. Since the system is otherwise the same as shown in Figure 1 the same reference numerals will be employed. In line 18 there is shown an inlet '33 for dry air.

In the operation of the system shown in Figure 3 oxygen to the extent of .05% by volume of the plating gases is bled into the system in a dry condition. When the gases passing from the carburetor 9 through line 18 containing the dry air from inlet 33 enter the chamber 19 the presence of oxygen tends to prohibit the formation of any copper metal.

The system of plating of Figure 1 is preferred to that of Figure 3. However in some instances it may be necessary to use a high temperature in the plating chamber thus raising the temperature of the ceramic to such an extent that metallic copper may tend to deposit. In this circumstance the air bleed of Figure 3 provides in the chamber suificient air to convert the copper to copper oxide. Where temperature conditions in the chamber are lower and more favorable the system of Figure l ofiers close control of the deposition and is preferred.

By way of illustration raising the temperaturepf the object to 650 F. and the temperature of the flowlng gas to 400 F. results in a substantially electrically non-conductive layer after 30 minutes exposure of the insulated object in the system of Figure 1. Thus by adjusting the flow temperature and/or the chamber atmosphere temperature, it is possible with relatively small temperature steps to attain layer resistance between 300 ohms and infinity.

A temperature rise in the chamber to 700 F. should be avoided with the system of Figure 1 however for metallic copper may then deposit.

The inert gases useful in the system of invention 1nclude, .as well ascarbon dioxide, argon, helium, nitrogen, etc.

Substantially all materials of heat insulating nature are suitable for the practice of the invention. Metallic objects however do not ingeneral maintain a sutfic1ently low surface temperature to permit the attainment of controlled resistive coatings in the flow ranges presently explored. Flow rates of between about 1 to liters of carrier gas per minute are however efiective with heat insulating materials and a particular flow condition may be readily chosen in conjunction with a specific carburetor temperature to attain a desired result.

This application is related to copending applications, Serial Nos. 250,301; 250,302; 250,304; 250,305; 250,306; and 250,307; all filed October 8, 1951, and all by the same inventor as the present application.

It will be understood that this invention is susceptible to modification in order to adopt it to different usages and conditions and accordingly, it is desired to comprehend such modifications within this invention as may fall within thescope of the appended claims.

I claim:

1. In a process of depositing copper oxide on heat insulating material the step of passing vapors of copper acetylacetonate together with an inert carrier gas heated to a temperature of less than about 450 F. over the insulating material maintained at a lower temperature than that at which said vapors decompose to metallic copper but above that of the vapors.

,2. In a process of depositing copper oxide on heat insulating material the step of passing mixed vapors of copper acetylacetonate and carbon dioxide at a temperature of less than about 450 F. over insulating material maintained at a lower temperature than that at which said vapors decompose to metallic copper but above that of the vapors.

3. In a process of depositing copper oxide on heat insulating material the steps of heating an atmosphere to a temperature of less than about 700 F. in a chamber, exposing the insulating material to the heat of said atmosphere, and passing vapors of a plating gas containing copper acetylacetonate and inert gas vapors at a temperature of less than about 450 F. over the heat insulating material at high flow rates of such a nature that temperature of the atmosphere and copper oxides are deposited by said atmosphere on said material.

4. A process for the formation of controlled amounts of the oxides of copper on heat insulating material comprising the steps of flowing a given quantity of heated carbon dioxide gas through layers of copper acetylacetonate maintained at a temperature of about 375 F. to form a given gaseous mixture having definite amounts of each gas at a temperature of about 375 F., and pressuring the gaseous mixture formed thereby through a heated chamber containing a ceramic material in an atmosphere having a temperature greater than that of said material and also greater than that of said flowing gaseous mixture, said gaseous mixture having a flow rate such that said insulating material does not attain the temperature of the said atmosphere and whereby said copper acetylacetonate decomposes depositing oxides of copper on said material in amounts proportioned to the flow rate of said given gaseous mixture.

5. process for the formation of controlled amounts of the oxides of copper on heat insulating materials comprismg the steps of flowing a given quantity of heated carbon dloxide gas through layers of copper acetylacetonate maintamed at a temperature of about 375 F. to form a given gaseous mixture having definite amounts of each gas therem at a temperature of about 375 F., and pressuring the gaseous mixture past a supply of dry air to draw a portron thereof into said mixture, and passing the pressured gases through a heated chamber containing a ceramic material having a temperature slightly above that necessary for the initiation of the decomposition of the copper acetylacetonate and below that at which the copper acetylacetonate decomposes to metallic copper at a flow rate of the gases such that said copper containing compound is decomposed and copper oxides are deposited on said material.

6. A process for the formation of an electrical resistance layer having a value of approximately 300 ohms comprising the steps of establishing an atmosphere at a temperature of about 600 F. at a distance of about A of an inch from a ceramic disc in the same atmosphere, and contacting the said disc with a flow of plating gas for about thirty minutes, said gas containing copper acetylacetonate and carbon dioxide and having a temperature of about 375 F. at substantially atmospheric pressure. 1

7. A process for the formation of an electrical resistance layer having a value of approximately infinite resistance compnsmgthe steps of establishing an atmosphere at a temperature of about 650 F. at a distance of about References Cited in the file of this patent Number UNITED STATES PATENTS Name Date Pilling Sept. 25, 1925 Groten July 28, 1936 Wheeler et al Mar. 19, 1940 Christensen June 2, 1942 Number 6 Name Date Lang Dec. 8, 1942 Drummond Oct. 19, 1943 Drummond Mar. 14, 1944 Marboe Nov. 11, 1947 Colbert et al. Mar. 21, 1950 Fink Nov. 27, 1951 Waggoner Dec. 11, 1951 Toulmin Jan. 1, 1952 OTHER REFERENCES American Institute of Metallurgical Engineers Technical Publication No. 2259, 1947 article by Lander et al. (only page 31 relied upon). 

1. IN A PROCESS OF DEPOSITING COPPER OXIDE ON HEAT INSULATING MATERIAL THE STEP OF PASSING VAPORS OF COPPER ACETYLACETONATE TOGETHER WITH AN INERT CARRIER GAS HEATED TO A TEMPERATURE OF LESS THAN ABOUT 450* F. OVER THE INSULATING MATERIAL MAINTAINED AT A LOWER TEMPERATURE THAN 